Wednesday 4 April 2012 16.32 EDT
First published on Wednesday 4 April 2012 16.32 EDT

Four New Orleans police officers have been sentenced to decades in prison over the killing of two people and wounding of four others fleeing the massive flooding of the city by hurricane Katrina.

A fifth officer was sent to jail for his role in a web of fabrications to cover up the true circumstances of the shootings on the Danziger bridge in 2005. The shootings came to symbolise the behaviour of a police force regarded as out of control in the chaotic aftermath of the hurricane which claimed nearly 2,000 lives and flooded about 80% of New Orleans.

The policemen were prosecuted in federal court after Louisiana state authorities declined to charge them. The federal investigation revealed a coverup that involved planted evidence, invented witnesses and falsified police reports that prosecutors said exposed a culture of corruption and a code of silence in the New Orleans police department.

Prosecutors described a force in disarray during the hurricane, with some officers dedicated to saving lives while others armed themselves with their own automatic weapons and behaved like vigilantes. Senior officers spread false assertions that martial law was declared and encouraged the shooting of looters.

Two officers – sergeants Kenneth Bowen and Robert Gisevius – were sentenced on Wednesday to 40 years in prison years for killing 17-year-old James Brissette and wounding four other people. Another officer, Anthony Villavaso, received 38 years for the same crime.

The court heard that Bowen used an unauthorised AK-47 to spray bullets at a group of civilians hiding behind a concrete barrier. Gisevius used a military-style M-4 rifle to shoot at unarmed people. Villavaso fired at least nine bullets at civilians with his AK-47.

A fourth policeman, Robert Faulcon, was sentenced to 65 years for killing Ronald Madison, a 40-year-old man with learning difficulties, by shooting him in the back with a shotgun. Madison's brother, Lance, was then arrested and accused of attempted murder after the police tried to cover up their actions by falsely accusing him of shooting at officers on the bridge. He was held in jail for three weeks before a court freed him.

Lance Madison told the court immediately before the sentencing that his brother was "gunned down and killed without mercy". He said to the convicted officers: "You are the reason I can no longer trust law enforcement."

The four officers were also convicted of an extensive coverup along with a former sergeant, Arthur Kaufman, who was not present when the shootings occurred. The coverup included the officers falsely claiming that they responded to a report of a fellow policeman having been shot and that at least four people opened fire on them when they arrived at the bridge. Kaufman will serve six years in prison.

Sherrel Johnson, Brissette's mother, repeated several times in an emotional statement directed at her son's killers: "I can't for the life of me understand what they were thinking."

Bowen's father, also called Kenneth, said he was proud of his son and that he had made a split-second decision and then acted "in what he thought was the best interest of the community".

The officers sentenced on Wednesday are among 20 policemen charged over killings, assaults and the fabrication of evidence during Katrina. Some have received lengthy sentences in earlier trials. Others pleaded guilty and gave evidence against former colleagues.

In a separate trial last year, three officers were convicted last year over the shooting a young black man and then burning his body in a car.

David Warren was sentenced to at least 25 years in prison for killing Henry Glover, 31. Another officer, Greg McRae, was sent to prison for 17 years for setting fire to a car with Glover's body in it in an apparent attempt to cover up Warren's crime.